There is no cure for homelessness. There are just too many causes for a single remedy to end this problem. However, we do know a lot about homelessness. And we can do a lot to treat this.
There is significant drug abuse, unemployment, legal problems with recidivism, poverty and lots of mental illness. In fact, as an emergency room physician who treats homeless patients every day, I see mental illness as either the direct cause or a major contributor to most who are homeless.
On my last shift, I treated a homeless psychotic patient out of his medications, a homeless schizophrenic woman with garbage bags she was using for shoes and a disheveled young man found down in a park due to a heroin overdose.